Conventionally, angle calibration of a rotary table of a machine tool is performed by: rotating the rotary table while a high-precision angle measuring system for calibration is attached to the rotary table; calculating, as a calibration value, the difference between a value of the angle of rotation detected by an angular sensor of the rotary table provided on the machine tool and a value measured by the high-precision angle measuring system; and inputting the calculated calibration value to a controller (for example, see PTL 1).